1. Field of the Invention
The present invention relates to a scroll compressor used, for example, as a refrigerant compressor for an air conditioning system for an automobile. In particular, the present invention relates to a device for blocking self-rotating movement of a movable scroll member in a scroll compressor.
2. Description of Related Art
Well known scroll compressors include a casing, a drive shaft rotatably supported by the casing, a fixed scroll member fixed with respect to the casing and a movable scroll member which is movable with respect to the casing and which is arranged eccentric with respect to an axis of the drive shaft and is driven by the drive shaft. The fixed and movable scroll members are in a side-by-side relationship to create closed chambers. Means are also provided for blocking the rotational movement of the movable scroll member about its own axis, while allowing an orbital movement of the movable scroll member about the axis of the drive shaft. The closed chambers are displaced radially inwardly while their volume is reduced during the orbital movement of the movable scroll member. An intake introduces a medium to be compressed into the chamber when the chamber is radially outwardly located. An outlet discharges the medium as compressed from the chamber when the chamber is radially inwardly located. The means for blocking self rotation comprises a plurality of angularly spaced circular recesses formed on the end surface of the movable scroll member facing the casing and the end surface of the casing facing the end surface of the scroll member, respectively. The recesses on each of the opposing end surfaces are arranged axially opposite each other, so that equiangularly spaced pairs of recesses are created on the movable scroll member and the casing. A plurality of spherical members are supported between the axially opposed recesses in the respective pairs. This self rotation blocking mechanism is defective in that the construction is itself complicated, thereby increasing the number of the parts. Furthermore, the provision of circular recesses necessarily requires a larger area for the end surfaces of the casing and the movable scroll members, thereby increasing the size as well as the weight of the related parts. This mechanism does not allow for the size and weight of the compressor to be reduced, on one hand, or for the manufacturing cost to be reduced, on the other hand.
A scroll compressor has been proposed wherein, angularly spaced pairs of axially opposed recesses, between which spherical members are supported, are replaced by angularly spaced crank pins arranged between the opposed end surfaces of the casing and the movable scroll member, respectively, as disclosed in the specification of DE-OS 3729319. Furthermore, Japanese Unexamined Patent Publication No. 57-203801 discloses a scroll compressor having a self rotation blocking mechanism in which angularly spaced pins are rotatably supported by means of respective needle bearings on an end plate of the movable scroll member. The pins engage a ring shaped groove formed on the opposed end surface of the casing. Furthermore, Japanese Unexamined Patent Publication No. 60-199983 discloses a self rotation blocking device for a scroll compressor, which device includes a plurality of angularly spaced, axially opposed pairs of pins connected to the opposed end surfaces of the movable scroll member and the casing, respectively, and a common ring engaged with the opposed pins of each pair.
The self rotation blocking mechanisms disclosed in these references are also defective in that the size of the mechanism is increased.